22 - Wrist Flexor Forearm Flashcards
What do I need to know?
- Bones of forearm and relation to wrist and elbow. Radio-ulnar joint and pronation/supination
- Compartments
- Flexor/pronator insertions, nerve supply, actions
- Wrist bones
- Disposition of the radial, median and ulnar nerves
What are the only intrinsic movements of the forearm?
Pronation and supination i.e. rotatory movements where the radius is moved in an arc medially around the ulna
During pronation/supination the radio-ulnar joints act as … while the interosseous membrane acts as a …
Pivots
Hinge
The hand can be rotated almost … degrees around the long axis of the limb
360 degrees
How are the forearm compartments formed?
MIS and LIS and interosseous membrane. The compartments are . not symmetrically arranged until the distal forearm
What muscles control the rotatory movements of the forearm?
Pronator Teres
Pronator Quadratus
Supinator
Describe the difference in cross section at the distal and proximal forearm
Distal: 4 compartments due to arm ext/flex tendons inserting. Sup/Pro compartments come in laterally/medially/obliquely
Proximal: Symmetrical posterior/supinator and anterior/pronator compartments
(EXCEPT anterior has 2x mass and 3x strength
Which bone is broader at superior radio-ulnar joint?
ULNA - radial head is smaller. Distally the radius is broad and ulna head is small. Are the same triangle shape midway
What is the fibrous articular disc attached to and what is its function?
> Attached to medial radius and houses the head of the ulna by connecting to the ulnar styloid process. Separates the inferior radio-ulnar joint from the true wrist joint. Means the ulna does NOT articulate in the wrist joint (DOES at elbow joint)
strengthens the joint
Purpose of the ulnar and radial styloid processes?
Bony spikes for ligaments to attach to
Ulnar Notch?
Houses the round small lateral head of the ulna
What does the fibrous articular disc attach to?
Medial radius > ulnar styloid process
What structures and joints allow pronation to occur?
- the proximal radius is held in place by the annular ligament while the distal radius rotates over the ulna at the inferior radio-ulnar joint permitted by the fibrous articular disc.
- hand articulates with RADIUS so takes it with it during pronation
Where would you find a sacciform recess at the wrist?
At the inferior radio-ulnar joint NOT the wrist joint. Above the fibrous articular disc
What is the carrying angle?
Angle of the forearm from the arm at elbow joint. Stops arms hitting hips while walking. Bigger than 15 degrees in females as have bigger hips, smaller than 15 in males as they have bigger chest
What are the 3 functions of the interosseous membrane?
- Flexible hinge during pronation/supination
- Muscle attachment
- Force transmission
How does the interosseous aid in force transmission?
If a force is applied to the wrist then the radius only is put under tension so all the force would be transduced and concentrated to the small head of the radius at the elbow. The membrane transmisses/dilutes the force to the broader ended ulna at the elbow. It resists compressive forces
How many carpal bones are there
8 in two rows of 4
How many joints are there at the wrist?
3
> Radio-carpal
> Mid-carpal
> Carpo-metacarpal
Radio-carpal joint?
Between radius and fibrous articular disc, and the distal row of carpal bones (Scaphoid, Lunate, Triquetral, not really Pisiform as is too medial/on top of triquetral)
> flexion/extension, abduction/adduction and SOME rotation
Mid-carpal joint?
> Between the 2 rows of carpals
> Some flexion/extension
Carpo-metacarpal joint?
VERY little movement EXCEPT at the thumb which is very mobile
> between carpals and metacarpa;s
Where does the flexor retinaculum span from and what does it form?
The most lateral > medial carpal bones (Scaphoid and Trapezium to Pisiform and Hamate)
> forms a concave Carpal Tunnel through which the tendons of the flexor muscles (except PL) enter
What bone is most likely to fracture at the wrist/radio-carpal joint?
Scaphoid as articulates with the radius the most
What does the flexor retinaculum prevent?
Bowstringing (bulge away) and holds tendons against the wrist to provide a mechanical advantage
How many Interphalangeal joints are there?
2 (proximal and distal) in fingers 1 in thumb
What is the palmar aponeurosis?
A triangular fibrous sheet fanning out from the distal flexor retinaculum
What tendon inserts into the palmar aponeurosis?
Palmaris longus after crossing over the flexor retinaculum
What muscles originate from the medial epicondyle?
- common flexor tendon
- NOT Pronator Teres, part of FDP, FPL has an ulnar origin
Superficial muscles?
4 - 1 = 3
- PT
- FCR
- PL
- FCU
Intermediate Muscle?
FDS
Deep muscles?
- FDP
- FPL
- PQ
Where does the Median Nerve run?
Runs through the cubital fossa and then runs between the 2 heads of pronator teres
Pronator Teres?
O: Medial supracondylar ridge
I: Superior lateral ulna
> pronates
> median nerve
Flexor Carpi Radialis?
O: Common flexor tendon
I: Base of the 2nd Metacarpal
> flex wrist
> median n
Palmaris Longus
O: Common Flexor Tendon
I: Palmar Aponeurosis to each finger (anchors skin of the palm as experiences a lot of shear forces)
> runs OVER flexor retinaculum and through the common synovial sheath of the palm
> 30% don’t have and weakly flexes wrist and interphalangeal joints
> Median n
Flexor Carpi Ulnaris
O: Common Flexor Tendon
I: Pisiform which is attached to the base of the 5th metatarsal
> ULNAR n
> flexes wrist
Flexor Digitorum Superficialis
O: > Radial head > Humero-ulnar head I: Split tendon inserts at the base of the MIDDLE phalynx of the digits > Median > can only flex PROXIMAL IP joint
Flexor Digitorum Profundus?
O: Anterior Ulna and Interosseous Membrane
I: Base of Distal Phalynx
> flexes distal IP joint (claw hand)
> half Median and Half Ulnar n
Flexor Pollicis Longus
O: Inferior half of ulna and inter oss I: Base of distal phalynx of thumb > flexing the thumb opposes the other fingers so needs own flexors > Median N > flex thumb
Hand has a … arterial supply
Dual
Pronator Quadratus?
Distal ulna > radius
> median n
> pronates
> is also an active stabiliser to keep the 2 bones together at their distal ends
Describe the course of the median nerve
- runs medial to biceps
- dives into cubital fossa beneath bicipital aponeurosis
- heads laterally through the 2 heads of PT
- gives of the Anterior Interosseous Nerve as it runs deep along the inteross memb
- median nerve continues in hand to give off palmar cutaneous nerve and RECURRENT branch
- terminates as proper palmar digital nerves
What does the median nerve and its branches supply?
Median: Superficial and intermediate > PT, FCR, PL, FDS Anterior Interosseous Nerve: Deep > FDP (half), FPL, PQ Palmar Cutaneous Branch Recurrent Branch > Lateral 2 lumbricals and Thenar Muscles Proper Palmar Digital Nerves
Does the Median Nerve run under or over the retinaculum?
UNDER
Describe the course of the Ulnar Nerve
- runs medially with median n and brachial artery until it runs posterior to MIS and medial epicondyle
- returns anteriorly between the heads of FCU
- gives off palmar cutaneous n
- gives off DORSAL cutaneous branch
- runs OVER the flexor retinaculum
- continues as deep branch ulnar nerve to supply most of the hand muscles
FDS acts as the … for the nerves and arteries
ROOF (ulnar nerve runs under this after passing between heads of FCU)
What does the ulnar nerve and its branches supply?
Ulnar: 1/2 FDP and FCU Palmar Cutaneous DORSAL Cutaneous Branch Deep Branch Ulnar > most intrinsic muscles of the hand Proper Palmar Digital Nerves
Where does the anterior interosseous nerve branch off and where do the interosseous arteries branch off?
Median Nerve
Ulnar Artery
Describe the course of the forearm arteries
> brachial artery divides in cubital fosaa to ulnar and radial
radial artery continues unbranched to wrist where it divides into deep/superficial branches
ulnar artery (may) divides into common interosseous artery and then continues into wrist to divide deep/superificial
CIA divides into anterior and posterior interosseous arteries. The anterior one runs with the ant inteross nerve from the MEDIAN nerve
the 2 interosseous arteries anastomose at the posterior distal forearm once anterior passes through a hole in membrane
What artery may be used for a bypass in the arm?
Radial artery - hand has dual supply and this artery has no/little branching. Only IF ulnar gives a good enough supply
The … artery acts as a boundary in the forearm. How?
Radial artery - anything medial to this artery is part of the flexor/pronator compartment and anything lateral is part of the extensor/supinator compartment
What artery is more important?
Ulnar
Which of the 2 interossei arteries is bigger?
The anterior due to ant comp having more muscle mass. Even sends perforating branches through to the posterior.
Most lateral structure at the carpal tunnel?
Radial Artery
Most medial structure at the carpal tunnel?
FCU
Carpal tunnel tendons, vessels and nerves lateral to medial
Radial Artery FCR FPL Median Nerve PL (NOT under ret) FDS FDP Ulnar Artery Ulnar Nerve FCU
Nerves or arteries more lateral at carpal tunnel?
Arteries
What arteries and nerves go THROUGH the carpal tunnel and which don’t?
Median Nerve does. NO arteries do (ulnar or radial). Ulnar nerve does NOT
What tendons does the median nerve run beside?
FDP medially and palmaris longus laterally
What MC are FDS and FDP in line with?
3rd metacarpal
